Re: [lwip-devel] [RFC PATCH 0/5] LWIP stack integration

[Tom Rini]

On Sun, Jun 11, 2023 at 09:24:14AM +0100, Simon Glass wrote:
> Hi,
> 
> On Wed, 7 Jun 2023 at 10:47, Ilias Apalodimas
> <ilias.apalodimas@linaro.org> wrote:
> >
> > Hi Maxim,
> >
> > On Tue, 6 Jun 2023 at 17:33, Maxim Uvarov <maxim.uvarov@linaro.org> wrote:
> > >
> > > Greetings,
> > >
> > > I implemented the tftp client (that was quick due to lwip has example app 
> > > for tftp), and did some more measurements.
> > > I uploaded patches here if somebody want to do his own measurements:
> > > https://github.com/muvarov/uboot-lwip
> > >
> > > measure 1:
> > > 976K - total (total means lwip with all 3 commands ping, tftp, wget)
> > > 971K - total - tftp  (total, but disable/minus tftp)
> > > 965K - total - tftp - wget (disable tftp and wget)
> > > 963K - total - tftp - wget - ping (disable tftp, wget, ping)
> > > 931K - no lwip
> > >
> > > result 1: lwip tftp (+ udp protocol) protocol 976-971k = 5kb
> > > result 2: lwip ping command 965- 963 = 2kb
> > > result 3: lwip wget command 971- 965 = 6kb
> > > result 4: lwip core stack with apps 976 - 931 = 45kb
> >
> > So tftp = 5kb, wget = 6kb ping =2kb and lwip = 32kb
> >
> > >
> > > measure 2:
> > > 890K - no CONFIG_NET_CMD
> > > 930K - + lwip tftp only
> > > 937K - + full lwip (ping wget tftp)
> > >
> > > result 1: 937-890=47kb ( lwip + all 3 commands)
> > > result 2: 937-930=7kb  (ping and lwip command)
> >
> > I am not sure I understand this measurement. How is this different
> > from measurement 1 where the entire binary was 976K?
> >
> > >
> > > measure 3:
> > > 904K - no lwip, CMD_NET_TFTP=y
> > > 900K - no lwip, CMD_NET_TFTP=n
> > > result 1: original u-boot tftp command 904-900=4kb
> > > 890K - no lwip, CMD_NET=n
> > > result 2: 900-890=10k original u-boot net/IP stack.
> > >
> > > My findings for all that measurements and lwip configuration:
> > > 1. The original u-boot net stack (packet process and up layers) is 10k vs 
> > > lwip 40k (the very minimal settings were 30k).
> > > 2. Network applications size is about the same 4kb for tftp original 
> > > command 5kb for lwip.
> > > 3. It's quite easy to reuse LWIP examples to implement the same 
> > > functionality for the U-boot.
> > > 4. I still think that there are other criterias which might have more 
> > > priority than size (bug free code, code reuse, development speed,  
> > > compatible API to posix and etc).
> >
> > Yes, there are other criteria and certainly having a complete network
> > stack might be worth it in many cases, but we need to keep in mind
> > 30kb might be a lot for some systems.
> >
> > I personally think this is decent and we can optimize lwip more in the
> > future.  Tom, Simon, how about adding lwip as 'experimental' and
> > making it depend on !CMD_NET or something similar?
> 
> That seems OK to me, but we don't really want two network stacks, so
> we'd need to set an expectation that we would move to lwip.

Yes, we'll need to move on to evaluating that once we can show and use
lwip as a replacement for most cases.

> I wonder why it is so large? I saw mention of it supporting multiple
> buffers and perhaps having a fuller implementation of the protocols.
> But it makes U-Boot's stack seem super-slim in comparison. I wonder if
> lwip could support just a single buffer and reduced functionality in
> other areas?

Well, right.  Seeing what space related tuneables we can introduce
and/or further tune down will be of interest.  But that will be easier
to do once it's easier to try out lwip in U-Boot itself.

-- 
Tom

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